分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We investigate the influence of active galactic nucleus (AGN) feedback on the galaxy cold gas content and its connection to galaxy quenching in three hydrodynamical simulations of Illustris, IllustrisTNG and SIMBA. By comparing to the observed atomic and molecular neutral hydrogen measurements for central galaxies, we find that Illustris over-predicts the cold gas masses in star-forming galaxies and significantly under-predicts them for quenched galaxies. IllustrisTNG performs better in this comparison than Illustris, but quenched galaxies retain too much cold gas compared with observations. SIMBA shows good agreement with observations, by depleting the global cold gas reservoir for quenched galaxies. We find that the discrepancies in IllustrisTNG are caused by its weak kinetic AGN feedback that only redistributes the cold gas from the inner disks to the outer regions and reduces the inner cold gas densities. It agrees with observations much better when only the cold gas within the stellar disk is considered to infer the star formation rates. From dependences of cold gas reservoir on the black hole mass and Eddington ratio, we find that the cumulative energy release during the black hole growth is the dominant reason for the cold gas depletion and thus the galaxy quenching. We further measure the central stellar surface density within 1 kpc ($\Sigma_1$) for the high-resolution run of IllustrisTNG and find a tight correlation between $\Sigma_1$ and black hole mass. It suggests that the observed decreasing trend of cold gas mass with $\Sigma_1$ is also a reflection of the black hole growth.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jiming Chen
Shamik Ghosh
Hao Liu
Larissa Santos
Wenjuan Fang
Siyu Li
Yang Liu
Hong Li
Jiaxin Wang
Le Zhang
Bin Hu
Wen Zhao
摘要： Constructing a fast and efficient estimator for the B-mode power spectrum of cosmic microwave background (CMB) is of critical importance for CMB science. For a general CMB survey, the Quadratic Maximum Likelihood (QML) estimator for CMB polarization has been proved to be the optimal estimator with minimal uncertainties, but it is computationally very expensive. In this article, we propose two new QML methods for B-mode power spectrum estimation. We use the Smith-Zaldarriaga approach to prepare pure-B mode map, and E-mode recycling method to obtain a leakage free B-mode map. We then use the scalar QML estimator to analyze the scalar pure-B map (QML-SZ) or B-mode map (QML-TC). The QML-SZ and QML-TC estimators have similar error bars as the standard QML estimators but their computational cost is nearly one order of magnitude smaller. The basic idea is that one can construct the pure B-mode CMB map by using the E-B separation method proposed by Smith-Zaldarriaga (SZ) or the one considering the template cleaning (TC) technique, then apply QML estimator to these scalar fields. By simulating potential observations of space-based and ground-based detectors, we test the reliability of these estimators by comparing them with the corresponding results of the traditional QML estimator and the pure B-mode pseudo-Cl estimator.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Ling Zhu
Annalisa Pillepich
Glenn van de Ven
Ryan Leaman
Lars Hernquist
Dylan Nelson
Ruediger Pakmor
Mark Vogelsberger
Le Zhang
摘要： Galactic dynamical structures are fossil records of the assembly histories of
galaxies. By analyzing the cosmological hydrodynamical simulation TNG50, we
find that a dynamical structure that we call the "hot inner stellar halo,"
defined by stars on dynamically hot orbits with circularity $\lambda_z < 0.5$
at $3.5\,{\rm kpc}
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The uncertainty in the photometric redshift estimation is one of the major
systematics in weak lensing cosmology. The self-calibration method is able to
reduce this systematics without assuming strong priors. We improve the recently
proposed self-calibration algorithm to enhance the stability and robustness
with the noisy measurement. The improved algorithm is tested on the power
spectra measured from the simulated catalogues constructed according to DECaLS
DR8 photometric catalogue. For the fiducial analysis with 5 equal-width
redshift bins over $0
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shamik Ghosh
Yang Liu
Le Zhang
Siyu Li
Junzhou Zhang
Jiaxin Wang
Jiazheng Dou
Jiming Chen
Jacques Delabrouille
Mathieu Remazeilles
Chang Feng
Bin Hu
Zhi-Qi Huang
Hao Liu
Larissa Santos
Pengjie Zhang
Zhaoxuan Zhang
Wen Zhao
Hong Li
Xinmin Zhang
摘要： AliCPT is the first Chinese cosmic microwave background (CMB) experiment which will make the most precise measurements of the CMB polarization in the northern hemisphere. The key science goal for AliCPT is the detection of primordial gravitational waves (PGWs). It is well known that an epoch of cosmic inflation, in the very early universe, can produce PGWs, which leave an imprint on the CMB in form of odd parity $B$-mode polarization. In this work, we study the performance of the component separation and parameter estimation pipelines in context of constraining the value of the tensor-to-scalar ratio. Based on the simulated data for one observation season, we compare five different pipelines with different working principles. Three pipelines perform component separation at map or spectra level before estimating $r$ from the cleaned spectra, while the other two pipelines performs a global fit for both foreground parameters and $r$. We also test different methods to account for the effects of time stream filtering systematics. This work shows that our pipelines provide consistent and robust constraints on the tensor-to-scalar ratio and a consistent sensitivity $\sigma(r) \sim 0.02$. This showcases the potential of precise $B$-mode polarization measurement with AliCPT-1. AliCPT will provide a powerful opportunity to detect PGWs, which is complementary with various ground-based CMB experiments in the southern hemisphere.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We measure the cross-correlation between galaxy groups constructed from DESI
Legacy Imaging Survey DR8 and \emph{Planck} CMB lensing, over overlapping sky
area of 16876 $\rm deg^2$. The detections are significant and consistent with
the expected signal of the large-scale structure of the universe, over group
samples of various redshift, mass, richness $N_{\rm g}$ and over various scale
cuts. The overall S/N is 40 for a conservative sample with $N_{\rm g}\geq 5$,
and increases to $50$ for the sample with $N_{\rm g}\geq 2$. Adopting the
\emph{Planck} 2018 cosmology, we constrain the density bias of groups with
$N_{\rm g}\geq 5$ as $b_{\rm g}=1.31\pm 0.10$, $2.22\pm 0.10$, $3.52\pm 0.20$
at $0.1
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shuren Zhou
Zhenjie Liu
Qinglin Ma
Yu Liu
Le Zhang
Xiao-Dong Li
Yang Wang
Xin Wang
Yu Yu
Hao-Ran Yu
Yi Zheng
摘要： We investigate impacts of massive neutrinos on the cosmic velocity fields, employing high-resolution cosmological $N$-body simulations provided by the information-optimized CUBE code, where cosmic neutrinos are evolved using collisionless hydrodynamics and their perturbations can be accurately resolved. In this study we focus, for the first time, on the analysis of massive-neutrino induced suppression effects in various cosmic velocity field components of velocity magnitude, divergence, vorticity and dispersion. By varying the neutrino mass sum $M_\nu$ from 0 -- 0.4 eV, the simulations show that, the power spectra of vorticity -- exclusively sourced by non-linear structure formation that is affected by massive neutrinos significantly -- is very sensitive to the mass sum, which potentially provide novel signatures in detecting massive neutrinos. Furthermore, using the chi-square statistic, we quantitatively test the sensitivity of the density and velocity power spectra to the neutrino mass sum. Indeed, we find that, the vorticity spectrum has the highest sensitivity, and the null hypothesis of massless neutrinos is incompatible with both vorticity and divergence spectra from $M_\nu=0.1$ eV at high significance ($p$-value $= 0.03$ and $0.07$, respectively). These results demonstrate clearly the importance of peculiar velocity field measurements, in particular of vorticity and divergence components, in determination of neutrino mass and mass hierarchy.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The peculiar velocities of dark matter halos are crucial to study many issues in cosmology and galaxy evolution. In this study, by using the state-of-the-art deep learning technique, a UNet-based neural network, we propose to reconstruct the peculiar velocity field from the redshift-space distribution of dark matter halos. Through a point-to-point comparison and examination of various statistical properties, we demonstrate that, the reconstructed velocity field is in good agreement with the ground truth. The power spectra of various velocity field components, including velocity magnitude, divergence and vorticity, can be successfully recovered when $k\lesssim 1.1$ $h/\rm Mpc$ (the Nyquist frequency of the simulations) at about 80% accuracy. This approach is very promising and presents an alternative method to correct the redshift-space distortions using the measured 3D spatial information of halos. Additionally, for the reconstruction of the momentum field of halos, UNet achieves similar good results. Hence the applications in various aspects of cosmology are very broad, such as correcting redshift errors and improving measurements in the structure of the cosmic web, the kinetic Sunyaev-Zel'dovich effect, BAO reconstruction, etc.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Time-ordered data (TOD) from ground-based CMB experiments are generally filtered before map-making to remove or reduce the contamination from the ground and the atmospheric emissions. However, when the observation region contains strong point sources, the filtering process will result in considerable leakage around the point sources in a measured CMB map, and leave spurious polarization signals. Therefore, such signals need to be assessed and removed before CMB science exploitation. In this work, we present a new method that we call "template fitting" and can effectively remove these leakage signals in pixel domain, not only satisfying the requirement for measuring primordial gravitational waves from CMB-$B$ modes, but also avoiding time-consuming operations on TOD.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The uncertainty in the photometric redshift estimation is one of the major
systematics in weak lensing cosmology. The self-calibration method is able to
reduce this systematics without assuming strong priors. We improve the recently
proposed self-calibration algorithm to enhance the stability and robustness
with the noisy measurement. The improved algorithm is tested on the power
spectra measured from the simulated catalogues constructed according to DECaLS
DR8 photometric catalogue. For the fiducial analysis with 5 equal-width
redshift bins over $0
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The peculiar velocities of dark matter halos are crucial to study many issues in cosmology and galaxy evolution. In this study, by using the state-of-the-art deep learning technique, a UNet-based neural network, we propose to reconstruct the peculiar velocity field from the redshift-space distribution of dark matter halos. Through a point-to-point comparison and examination of various statistical properties, we demonstrate that, the reconstructed velocity field is in good agreement with the ground truth. The power spectra of various velocity field components, including velocity magnitude, divergence and vorticity, can be successfully recovered when $k\lesssim 1.1$ $h/\rm Mpc$ (the Nyquist frequency of the simulations) at about 80% accuracy. This approach is very promising and presents an alternative method to correct the redshift-space distortions using the measured 3D spatial information of halos. Additionally, for the reconstruction of the momentum field of halos, UNet achieves similar good results. Hence the applications in various aspects of cosmology are very broad, such as correcting redshift errors and improving measurements in the structure of the cosmic web, the kinetic Sunyaev-Zel'dovich effect, BAO reconstruction, etc.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Calibrating the redshift distributions of photometric galaxy samples is essential in weak lensing studies. The self-calibration method combines angular auto- and cross-correlations between galaxies in multiple photometric redshift (photo-$z$) bins to reconstruct the scattering rates matrix between redshift bins. In this paper, we test a recently proposed self-calibration algorithm using the DECaLS Data Release 9 and investigate to what extent the scattering rates are determined. We first mitigate the spurious angular correlations due to imaging systematics by a machine learning based method. We then improve the algorithm for $\chi^2$ minimization and error estimation. Finally, we solve for the scattering matrices, carry out a series of consistency tests and find reasonable agreements: (1) finer photo-$z$ bins return a high-resolution scattering matrix, and it is broadly consistent with the low-resolution matrix from wider bins; (2) the scattering matrix from the Northern Galactic Cap is almost identical to that from Southern Galactic Cap; (3) the scattering matrices are in reasonable agreement with those constructed from the power spectrum and the weighted spectroscopic subsample. We also evaluate the impact of cosmic magnification. Although it changes little the diagonal elements of the scattering matrix, it affects the off-diagonals significantly. The scattering matrix also shows some dependence on scale cut of input correlations, which may be related to a known numerical degeneracy between certain scattering pairs. This work demonstrates the feasibility of the self-calibration method in real data and provides a practical alternative to calibrate the redshift distributions of photometric samples.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Low Density Points (LDPs, \citet{2019ApJ...874....7D}), obtained by removing
high-density regions of observed galaxies, can trace the Large-Scale Structures
(LSSs) of the universe. In particular, it offers an intriguing opportunity to
detect weak gravitational lensing from low-density regions. In this work, we
investigate tomographic cross-correlation between Planck CMB lensing maps and
LDP-traced LSSs, where LDPs are constructed from the DR8 data release of the
DESI legacy imaging survey, with about $10^6$-$10^7$ galaxies. We find that,
due to the large sky coverage (20,000 deg$^2$) and large redshift depth ($z\leq
1.2$), a significant detection ($10\sigma$--$30\sigma$) of the CMB lensing-LDP
cross-correlation in all six redshift bins can be achieved, with a total
significance of $\sim 53\sigma$ over $ \ell\le1024$. Moreover, the measurements
are in good agreement with a theoretical template constructed from our
numerical simulation in the WMAP 9-year $\Lambda$CDM cosmology. A scaling
factor for the lensing amplitude $A_{\rm lens}$ is constrained to $A_{\rm
lens}=1\pm0.12$ for $z<0.2$, $A_{\rm lens}=1.07\pm0.07$ for $0.2
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We investigate the influence of active galactic nucleus (AGN) feedback on the galaxy cold gas content and its connection to galaxy quenching in three hydrodynamical simulations of Illustris, IllustrisTNG and SIMBA. By comparing to the observed atomic and molecular neutral hydrogen measurements for central galaxies, we find that Illustris over-predicts the cold gas masses in star-forming galaxies and significantly under-predicts them for quenched galaxies. IllustrisTNG performs better in this comparison than Illustris, but quenched galaxies retain too much cold gas compared with observations. SIMBA shows good agreement with observations, by depleting the global cold gas reservoir for quenched galaxies. We find that the discrepancies in IllustrisTNG are caused by its weak kinetic AGN feedback that only redistributes the cold gas from the inner disks to the outer regions and reduces the inner cold gas densities. It agrees with observations much better when only the cold gas within the stellar disk is considered to infer the star formation rates. From dependences of cold gas reservoir on the black hole mass and Eddington ratio, we find that the cumulative energy release during the black hole growth is the dominant reason for the cold gas depletion and thus the galaxy quenching. We further measure the central stellar surface density within 1 kpc ($\Sigma_1$) for the high-resolution run of IllustrisTNG and find a tight correlation between $\Sigma_1$ and black hole mass. It suggests that the observed decreasing trend of cold gas mass with $\Sigma_1$ is also a reflection of the black hole growth.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jinyi Liu
Zeyang Sun
Jiakang Han
Julien Carron
Jacques Delabrouille
Siyu Li
Yang Liu
Jing Jin
Shamik Ghosh
Bin Yue
Pengjie Zhang
Chang Feng
Zhi-Qi Huang
Hao Liu
Yi-Wen Wu
Le Zhang
Zi-Rui Zhang
Wen Zhao
Bin Hu
Hong Li
摘要： AliCPT-1 is the first Chinese CMB experiment aiming for high precision
measurement of Cosmic Microwave Background B-mode polarization. The telescope,
currently under deployment in Tibet, will observe in two frequency bands
centered at 90 and 150 GHz. We forecast the CMB lensing reconstruction,
lensing-galaxy as well as lensing-CIB (Cosmic Infrared Background) cross
correlation signal-to-noise ratio (SNR) for AliCPT-1. We consider two stages
with different integrated observation time, namely "4 module*yr" (first stage)
and "48 module*yr" (final stage). For lensing reconstruction, we use three
different quadratic estimators, namely temperature-only, polarization-only and
minimum-variance estimators, using curved sky geometry. We take into account
the impact of inhomogeneous hit counts as well as of the mean-field bias due to
incomplete sky coverage. In the first stage, our results show that the 150 GHz
channel is able to measure the lensing signal at $15\sigma$ significance with
the minimum-variance estimator. In the final stage, the measurement
significance will increase to $31\sigma$. We also combine the two frequency
data in the harmonic domain to optimize the SNR. Our result show that the
coadding procedure can significantly reduce the reconstruction bias in the
multiple range l>800. Thanks to the high quality of the polarization data in
the final stage of AliCPT-1, the EB estimator will dominate the lensing
reconstruction in this stage. We also estimate the SNR of cross-correlations
between AliCPT-1 CMB lensing and other tracers of the large scale structure of
the universe. For its cross-correlation with DESI galaxies/quasars, we report
the cross-correlation SNR = 10-20 for the 4 redshift bins at 0.05
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Time-ordered data (TOD) from ground-based CMB experiments are generally filtered before map-making to remove or reduce the contamination from the ground and the atmospheric emissions. However, when the observation region contains strong point sources, the filtering process will result in considerable leakage around the point sources in a measured CMB map, and leave spurious polarization signals. Therefore, such signals need to be assessed and removed before CMB science exploitation. In this work, we present a new method that we call "template fitting" and can effectively remove these leakage signals in pixel domain, not only satisfying the requirement for measuring primordial gravitational waves from CMB-$B$ modes, but also avoiding time-consuming operations on TOD.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Calibrating the redshift distributions of photometric galaxy samples is essential in weak lensing studies. The self-calibration method combines angular auto- and cross-correlations between galaxies in multiple photometric redshift (photo-$z$) bins to reconstruct the scattering rates matrix between redshift bins. In this paper, we test a recently proposed self-calibration algorithm using the DECaLS Data Release 9 and investigate to what extent the scattering rates are determined. We first mitigate the spurious angular correlations due to imaging systematics by a machine learning based method. We then improve the algorithm for $\chi^2$ minimization and error estimation. Finally, we solve for the scattering matrices, carry out a series of consistency tests and find reasonable agreements: (1) finer photo-$z$ bins return a high-resolution scattering matrix, and it is broadly consistent with the low-resolution matrix from wider bins; (2) the scattering matrix from the Northern Galactic Cap is almost identical to that from Southern Galactic Cap; (3) the scattering matrices are in reasonable agreement with those constructed from the power spectrum and the weighted spectroscopic subsample. We also evaluate the impact of cosmic magnification. Although it changes little the diagonal elements of the scattering matrix, it affects the off-diagonals significantly. The scattering matrix also shows some dependence on scale cut of input correlations, which may be related to a known numerical degeneracy between certain scattering pairs. This work demonstrates the feasibility of the self-calibration method in real data and provides a practical alternative to calibrate the redshift distributions of photometric samples.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Yongheng Zhou
Kaiyue He
Huamin Hu
Gang Ouyang
Chao Zhu
Wei Wang
Sichen Qin
Ye Tao
Runfeng Chen
Le Zhang
Run Shi
Chun Cheng
Han Wang
Yanjun Liu
Zheng Liu
Taihong Wang
Wei Huang
Lin Wang
Xiaolong Chen
摘要： Magneto-optical effect has been widely used in light modulation, optical sensing and information storage. Recently discovered two-dimensional (2D) van der Waals layered magnets are considered as promising platforms for investigating novel magneto-optical phenomena and devices, due to the long-range magnetic ordering down to atomically-thin thickness, rich species and tunable properties. However, majority 2D antiferromagnets suffer from low luminescence efficiency which hinders their magneto-optical investigations and applications. Here, we uncover strong light-magnetic ordering interactions in 2D antiferromagnetic MnPS3 utilizing a newly-emerged near-infrared photoluminescence (PL) mode far below its intrinsic bandgap. This ingap PL mode shows strong correlation with the Neel ordering and persists down to monolayer thickness. Combining the DFT, STEM and XPS, we illustrate the origin of the PL mode and its correlation with Neel ordering, which can be attributed to the oxygen ion-mediated states. Moreover, the PL strength can be further tuned and enhanced using ultraviolet-ozone treatment. Our studies offer an effective approach to investigate light-magnetic ordering interactions in 2D antiferromagnetic semiconductors.
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